2.1 Study site
The study site was located in Siziwang Banner (41°46′43.6″ N, 111°53′41.7″ E, 1456 m a.s.l.) in Inner Mongolia, northern China. The region has a temperate continental arid and semi-arid climate, which is dry and windy in spring and hot in summer. Mean annual precipitation was 220.00 mm and mean annual temperature was 3.80 °C (from 2004 to 2018). Minimum temperature was -16.22 °C in January and maximum temperature was 21.14 °C in July (from 2004 to 2018). Rainfall is mainly concentrated in May to August, with a humidity of 15% to 30%. The frost-free period is 175 days. The main soil type is calcic Kastanozem (FAO soil classification). Soil texture is sandy loam with 71.23±3.98% sand, 15.97±2.87% silt, and 12.81±2.69% clay. The total carbon, total nitrogen, available nitrogen, available phosphorus, available potassium and pH were 13.56 g·kg-1, 1.41 g·kg-1, 8.08 g·kg-1, 8.30 mg·kg-1, 50.58 g·kg-1 and 10.57, respectively. The vegetation in the desert steppe is dominated byStipa breviflora, Artemisia frigida , andCleistogenes songorica, with average vegetation height of 8 cm and a canopy cover ranging from 17% to 20%.